vct/vvt when turbo'd

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furryeggs
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vct/vvt when turbo'd

Post by furryeggs » Tue Apr 29, 2014 10:45 pm

I been trying to find out what happens to the vct/vvt when a turbo conversion's done on the 1.7. how is it controlled when a seperate ecu is used ie megasquirt? or is it not used when turbo'd.
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Re: vct/vvt when turbo'd

Post by Cartman » Wed Apr 30, 2014 7:22 am

you can stil use the vct whit a turbo, no real problem there, the only real issue, is finding an aftermarket ecu that can controll it, and actualy mapping it so it works propperly :)
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Re: vct/vvt when turbo'd

Post by PumaNoob » Wed Apr 30, 2014 10:48 am

Or you could do as im doing, and hook up the cam sensor, TPS and an RPM signal to the stock ECU, run 2 ECU's and have the stock ECU run the VCT, and have your after market ECU just run fuel and spark.

I hooked up an LED to the VCT solenoid on my onld car when i was running aftermarket ECU, and it still functioned. However im still not entirely sure exactly what triggers it, if its just RPM, or if it needs TPS, MAF, or cam sensor signal to run. At a guess id say that if you dont plug the cam sensor into it, it will go into a default setting using just rpm and possibly TPS.

But any info you find on this id be interested in your findings as im doing the same thing but with a different engine.

Some people dont use the VCT on turbo conversions, but when i tried it on the 1.7 it made a huge difference miid range, it just didnt pick up as well without VCT and wasnt as lively!
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Re: vct/vvt when turbo'd

Post by Cartman » Wed Apr 30, 2014 11:58 am

PumaNoob's methode is actualy quite briliant :) and is probably the easyest way to make it work :)

as for what sensors it needs, it is my belife that the VCT is reliant on the calculated engien load, as it's purpous is to give the most torqe at every rpm, I'm not entierly shure, but I think it uses all the sensors, ie speed, cam, maf, and so on, and ajusts acordingly..
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Re: vct/vvt when turbo'd

Post by PumaNoob » Wed Apr 30, 2014 12:08 pm

It would make sense that it's calculate on load, but if that is the case and it needs inputs from all sensors, then I'm going to have to rethink my set up as I have no MAF with the after market set up. But that's not to say I can't take a MAF apart and put it somewhere in my inlet tubing so the standard ECU can make a calculation from it. Hopefully my car will be back on the rd soon so I can see if my set up works. My guess would be, if I increase the intake pipe flow area in proportion to the engine size increase, then the ECU will see near the same flow on my new engine at roughly the same RPM. Then I can tweak it from there! I'll have a whole lot of fun trying it!
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Re: vct/vvt when turbo'd

Post by Wild E. Coyote » Wed Apr 30, 2014 3:27 pm

PumaNoob wrote:It would make sense that it's calculate on load, but if that is the case and it needs inputs from all sensors, then I'm going to have to rethink my set up as I have no MAF with the after market set up. But that's not to say I can't take a MAF apart and put it somewhere in my inlet tubing so the standard ECU can make a calculation from it. Hopefully my car will be back on the rd soon so I can see if my set up works. My guess would be, if I increase the intake pipe flow area in proportion to the engine size increase, then the ECU will see near the same flow on my new engine at roughly the same RPM. Then I can tweak it from there! I'll have a whole lot of fun trying it!
Have a look at this. Might be interesting…. http://www.projectpuma.com/viewtopic.ph ... it=VCT+ECU" onclick="window.open(this.href);return false;

or in short: http://www.motorsport-electronics.co.uk" onclick="window.open(this.href);return false;
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Re: vct/vvt when turbo'd

Post by PumaNoob » Wed Apr 30, 2014 3:38 pm

That's perfect!! But I can't open the details or see prices on my phone, I'll take a look when I get home.

On a side note the megasquirt 3 v3 ECU's do support full VCT control. Trigger wheels are megasquirt suppliers so its probably the same technology. My MS2 is able to support one PWM output, but it can be used for either idle or VCT, but you cant have both.

EDIT: Ive just seen the price, with a loom its nearly £300 :o with a cheap ECU and that, it dont work out so cheap any more, so id probably just go with the later megasquirt with VCT control!
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Re: vct/vvt when turbo'd

Post by Ziggy » Thu May 01, 2014 1:45 pm

Adjustment of 1.7 VCT is controlled by ECU using engine load (throttle pot and MAF) and engine speed (crank position sensor). The CAM adjustment angle is monitored using the crank and cam position sensors using a 3D map. It also uses engine temp and air temp to delay activation until suitable engine temperatures are reached - now a 4D adjustment map. Note the adjustment angle limit increases as these temps increase up to a predetermined threshold.

The standard ECU and MAF sensor will be totally overwhelmed with charge boost - thats why you need a MAP sensor and aftermarket ECU in order for the engine to determine load and provide suitable fuel / ignition.

The question of whether you actually need to change cam timing in order to increase valve overlap on a turbo engine is an entirely different matter. Try with and without VCT on a fully mapped engine on an engine dyno and go with the the one most suitable for you requirements.
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Re: vct/vvt when turbo'd

Post by furryeggs » Fri May 02, 2014 10:24 pm

Do you also need to retard the ignition, is that done in the ecu as well, or by angle adjustment from Top dead centre, or is that just on carb'd engines.
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Re: vct/vvt when turbo'd

Post by Wild E. Coyote » Sat May 03, 2014 5:57 am

Spark map is much more complex than that, I'd say, especially on a modern fuel injected engine. It is calculated based on speed of engine, load, temperature, knock sensor (always hanging on the maximum advance possible) and probably on return info from lambda as well.
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Re: vct/vvt when turbo'd

Post by PumaNoob » Sat May 03, 2014 10:20 am

Yes, generally speaking, spark timing needs to be retarded on boost, but there are loads of variables, engine speed, air temp, dynamic compression ratio ect.

And VCT is always going to be an advantage on a turbo engine, as long as the correct cams are selected, because turbo cams are normally short duration, the VCT will allow it to be more efficient at low and and high end instead of compramising. But, sometimes the gain is going to be very minimal and not worth the effort or hassle. I dont think the gains will be a lot in my engine, but its worth doing for me as its available so rude not to try and utilise it :lol:

The VCT may not be used to increase overlap. the system is set up retarded, so when it advances the cam, it may only be going to optimal settings. So essentially it is only setting the cam to standard settings low down, and then reducing overlap when the cylinder pressures build up. The cam doesnt work like most people assume it does. It advances low down and then slowly retards as the revs increase. So potentially it will be an advantage on any engine.
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Re: vct/vvt when turbo'd

Post by furryeggs » Sun May 04, 2014 4:38 pm

so fit an aftermarket ecu capable of running vct/vvt and the map will take care of retarding at higher revs and smooth out low end?
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Re: vct/vvt when turbo'd

Post by PumaNoob » Mon May 05, 2014 1:10 pm

Yes, you'd have to put it on a dyno to get the settings optimal. For my set up with standard cams, there was a noticeable difference mid range with the VCT. That's not to say that it would have been so noticeable with a different set of cams. There are just too many variables to calculate what the outcome of a set amount of advance or retard might do. But all the modern ford ecoboost engines use VCT, or TiVCT. Again, sometimes the hassle of setting it all up and the costs can outweigh the benifits
& gains.
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Re: vct/vvt when turbo'd

Post by bundy_zs » Tue Jul 01, 2014 9:24 am

Hey guys, I also have been thinking about how I can use the VCT to my advantage. I thought about making totally manual with a micro-controller and transistor circuit to create a simple PWM circuit which would alter the duty cycle of the solenoid. Another idea I had was to read the duty cycle of the solenoid with a similar circuit and make it so I knew where the VCT was at any point in time.

My question though comes from the position of the cams. In order to see any gains low down in the rpm range, the cam would have to be fully advanced when you first start the car. How is this achieved, does the ECU wait until sufficient oil pressure is built up whilst cranking to be able fully advance the cam?

(The reason I ask is because I have just reset the timing on my puma engine and noticed how the cam is fully retarded when it is back against its stop to allow you to put the timing bar in, so it is already in the high rpm setting, and when you turn the engine over by hand it stays there, so it must need sufficient oil pressure to overcome this)
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Re: vct/vvt when turbo'd

Post by PumaNoob » Tue Jul 01, 2014 10:23 am

That would be great if you could alter it for your own particular set up. There are units already available for this but are quite expensive.

The hard part is data logging it, if it's just RPM based then it would be easy, but if it's load dependant, you would have to log a few things, at the very least,you'd need to log throttle position, rpm, and pulse width. I'm sure a clever person (cleverer then me) could do it).

And to answer your question, ford don't advance the cam on idle, there is a small pulse width at the sensor, but it's not 100%. I believe this is down to emissions. To advance the cam on idle would increase idle power output, and so to to keep the engine running smooth, they would have to increase fuelling, so idle emissions and fuel consumption would suffer. I was always lead to believe that you don't tune idle for power, because the only way is down from there, and you are more likely to get a flat spot when accelerating away. It could be myth, I don't know but it's a principal I've used and it's worked fine. I've tuned my car so it passes MOT emissions without a cat.

So I believe the cam fully advances around 1800rpm, then slowly retards up until around 4000-4500 (at a guess).

ISAs going to install a 12v LED to mine, so I'd have a visual idea of how it was working, although I doubt I'd be able to tell the difference between an 80% duty and 100% duty.
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Re: vct/vvt when turbo'd

Post by Wild E. Coyote » Tue Jul 01, 2014 11:38 am

bundy_zs wrote:Hey guys, I also have been thinking about how I can use the VCT to my advantage. I thought about making totally manual with a micro-controller and transistor circuit to create a simple PWM circuit which would alter the duty cycle of the solenoid. Another idea I had was to read the duty cycle of the solenoid with a similar circuit and make it so I knew where the VCT was at any point in time.

My question though comes from the position of the cams. In order to see any gains low down in the rpm range, the cam would have to be fully advanced when you first start the car. How is this achieved, does the ECU wait until sufficient oil pressure is built up whilst cranking to be able fully advance the cam?

(The reason I ask is because I have just reset the timing on my puma engine and noticed how the cam is fully retarded when it is back against its stop to allow you to put the timing bar in, so it is already in the high rpm setting, and when you turn the engine over by hand it stays there, so it must need sufficient oil pressure to overcome this)
I think you may have misunderstood this. Pumanoob has partially answered you question. But at idleing the cam is fully retarded and restign in its let's say zero (as VCT isn't doing anything) position.
Please, do read this. http://motorsport-electronics.co.uk/for ... 8&t=11#p16" onclick="window.open(this.href);return false;
It will take about 10 minutes of your time, but it is very informative. Also, bear in mind, as Pumanoob has already said, that (the map or graph showing the variation in cam phasing is occuring at 100% throttle there!) this is also done because of emissions. So, at partial load the graph would most probably be different. The cam phasing is VERY complicated thing if you want to do it right. Also, have you ever asked yourself how comes it is at inlet side of the engine? Because you can do internal gas recirculation; by leaving the inlet valves open longer you can let some of the gasses in inlet and then use it again on next cycle...
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